Flat-oval duct-forming machines of the prior art have had minor-axis compaction surfaces which have been flat, requiring heavy, expensive steel construction to provide strength against the bending of the compaction surfaces out of shape. The heavy weight requirement has kept high the steel cost for such machines and also has increased the shipping costs. But the major problem with flat-surfaced minor-axis compactors has been the danger of duct leakage in the finished duct. This is because such ducts are made from cylindrical stock having circumferential spiraling strips of metal which are interlocked at their edges. Such interlocked seams are normally capable of withstanding leakage. However, when such ducts are shaped by a flat-oval duct-shaping machine of the flat minor-axis compacting surface type, then a great stress is placed on the duct seams which causes deformation at the seams and leakage danger.
It is, therefore, an objective hereof to provide a duct-forming machine having compacting surfaces which are curved because I have found that this does not deform the seams as greatly as flat-surfaced compactors, whereby duct leakage is eliminated.
Another objective of this invention is to reduce the cost and the weight of flat-oval duct-forming machine minor-axis compactors by providing light, hollow, braced minor-axis compactors each having a convex compaction surface held in place by a flat backside steel sheet fixed thereto.
Other objectives are to provide for adjustment to fit different sizes of ducts.
Yet another objective is to provide a way to place a heavy cylindrical duct work-piece onto the machine by raising an upper major-axis pressing module at one end by the use of a pipe attached to a same fork-lift truck that delivers the heavy cylindrical work-piece to the shaping machine.
Still another objective is to provide for the placement of a duct work-piece onto the machine by having the upper major axis pressing module pivotally mounted on the frame adjacent one end thereof and having means for providing a rotational course on the upper module so as to cause it to swing upwardly at its other end onto which the cylindrical duct work-piece is then loaded. This force can be applied by a hydraulic cylinder assembly or by many other automatic means, such as, for example, a gear operated motor, so that at the push of a button, the operator can cause the duct receiving end of the upper pressing module to raise up to receive a duct, and at another pressing of a button can lower again into duct-shaping position.
Further objectives are to provide a pulley-hoist system for quick and minute vertical adjustments of the minor-axis compaction assembly with respect to upper and lower pressing modules, and the compactors each having a pivotal connection with the remainder of the compactor assembly along horizontal lines for automatic positioning by engagement of their convex surfaces with the duct.
Other objectives are for the modules each to be composed of a beam on which covers can be replaceably disposed by sliding them out and off of the beam swiftly without any bolts or attachments, the covers being stabilized by their weight and by gravity in cooperation with retainers and positioners attached to the covers and engageable with the beam.
Yet a further objective is to provide for an upper one of the modules to be supported between its ends on posts by a vertically adjustable keeper so that a new duct can be placed on the upper module while it is supported only by the keeper and by an hydraulic assembly at the opposite end of the upper module from its loading end so as to make use of a forklift truck unnecessary for upper module support during loading.
Another objective is for each beam to have a plurality of vertical webs connected to horizontal flanges for stiffness and strength under great pressure.